Summary
A Global Positioning System (GPS) survey has been carried out on the Amery Ice Shelf, providing "ground-truth" measurements of ellipsoidal height for the ERS-1 and ERS-2 satellite altimeters. A 120 km by 20 km grid made up of 10 km squares was established on the ice shelf using kinematic GPS techniques. A local tidal signal was subtracted from the GPS data, producing profiles relative to a tide-free surface. Contemporaneous ERS altimeter waveform data over the survey region were retracked and tide-corrected, producing altimetric height profiles. Two approaches were used for comparison. Firstly, GPS and altimeter heights were compared at intersecting points of the two types of surface profiles. Secondly, a gridded surface was generated from the GPS data and resulting surface heights compared with altimeter heights along the satellite ground tracks. In both cases the combined mean and RMS of the height differences over the region were 0.2 m and 1.7 m respectively. Along individual profiles, the RMS difference was 0.5 m where the surface was relatively flat, and 2.9 m where it was more topographically variable. The survey has provided an excellent "ground truthing" reference surface for ERS altimeter data, which are being used within the Antarctic CRC to generate a precise, high resolution digital elevation model for the Lambert Glacier - Amery Ice Shelf system.